[PATCH 3.16 73/87] scsi: vmw_pscsi: Fix use-after-free in pvscsi_queue_lck()

[Ben Hutchings]

3.16.75-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Jan Kara <jack@xxxxxxx>

commit 240b4cc8fd5db138b675297d4226ec46594d9b3b upstream.

Once we unlock adapter->hw_lock in pvscsi_queue_lck() nothing prevents just
queued scsi_cmnd from completing and freeing the request. Thus cmd->cmnd[0]
dereference can dereference already freed request leading to kernel crashes
or other issues (which one of our customers observed). Store cmd->cmnd[0]
in a local variable before unlocking adapter->hw_lock to fix the issue.

Signed-off-by: Jan Kara <jack@xxxxxxx>
Reviewed-by: Ewan D. Milne <emilne@xxxxxxxxxx>
Signed-off-by: Martin K. Petersen <martin.petersen@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/scsi/vmw_pvscsi.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/scsi/vmw_pvscsi.c
+++ b/drivers/scsi/vmw_pvscsi.c
@@ -754,6 +754,7 @@ static int pvscsi_queue_lck(struct scsi_
 	struct pvscsi_adapter *adapter = shost_priv(host);
 	struct pvscsi_ctx *ctx;
 	unsigned long flags;
+	unsigned char op;
 
 	spin_lock_irqsave(&adapter->hw_lock, flags);
 
@@ -766,13 +767,14 @@ static int pvscsi_queue_lck(struct scsi_
 	}
 
 	cmd->scsi_done = done;
+	op = cmd->cmnd[0];
 
 	dev_dbg(&cmd->device->sdev_gendev,
-		"queued cmd %p, ctx %p, op=%x\n", cmd, ctx, cmd->cmnd[0]);
+		"queued cmd %p, ctx %p, op=%x\n", cmd, ctx, op);
 
 	spin_unlock_irqrestore(&adapter->hw_lock, flags);
 
-	pvscsi_kick_io(adapter, cmd->cmnd[0]);
+	pvscsi_kick_io(adapter, op);
 
 	return 0;
 }